Removal of free formaldehyde from solutions of methylolated carbamatefinishing agents and textiles treated therewith

ABSTRACT

THE FREE FORMALDEHYDE CONTENT OF A SOLUTION OF METHYLOLATED CARBAMATE FINISHING AGENT IS REDUCED BY REMOVAL OF FREE FORMALDEHYDE THROUGH REACTION WITH PHTHALIMIDE TO GIVE AN INSOLUBLE PHTHALIMIDE-FORMALDEHYDE ADDUCT THAT IS READILY SEPARATED FROM THE SOLUTION. FABRIC SENSITIZED BY TREATMENT WITH THE SP-MODIFIED SOLUTION HAS A LOW LEVEL OF FORMALDEHYDE RELEASE. WHEN THE SENSITIZED FABRIC IS CURED, THE RESULTANT FABRIC IS WRINKLE RESISTANT AND EXHIBITS ALL THE OTHER PROPERTIES CHARACTERISTIC OF THE CARBAMATE FINISH.

Patented Mar. 27, 1973 REMOVAL OF FREE FORMALDEHYDE FROM SOLUTIONS OFMETHYLOLATEI) CARBA- MATE FINISHING AGENTS AND TEXTILES TREATEDTHEREWITH Robert M. Reinhardt, New Orleans, and Russell M. H. Kullman,Metairie, La., assignors to the United States of America as representedby the Secretary of Agriculture No Drawing. Filed Apr. 27, 1972, Ser.No. 248,187

Int. Cl. D06m 15/58 U.S. Cl. 8-182 3 Claims ABSTRACT OF THE DISCLOSUREThe free formaldehyde content of a solution of methylolated carbamatefinishing agent is reduced by removal of free formaldehyde throughreaction with phthalimide to give an insoluble phthalimide-formaldehydeadduct that is readily separated from the solution. Fabric sensitized bytreatment with the so-modified solution has a low level of formaldehyderelease. When the sensitized fabric is cured, the resultant fabric iswrinkle resistant and exhibits all the other properties characteristicof the carbamate finish.

A nonexclusive, irrevocable, royalty-free license in the inventionherein described, throughout the world for all purposes of the UnitedStates Government, with the power to grant sublicenses for suchpurposes, is hereby granted to the Government of the United States ofAmerica.

FIELD TO WHICH INVENTION RELATES This invention relates to a process forremoving and thereby decreasing the amount of free formaldehyde insolutions of carbamate finishing agents. The so-modified solutions aresuitable for use in finishing treatments to impart wrinkle resistance totextile materials. More specifically, the invention relates to a methodof reducing the amount of free formaldehyde in solutions of carbamatefinishing agents by reaction of free formaldehyde with phthalimide. Thisreaction gives an insoluble adduct that is readily separated from thesolution of the finishing agent to reduce the free formaldehyde contentthereof. The invention also relates to the use of the so-modifiedsolutions of carbamate finishing agents to give sensitized fabrics withgreatly decreased levels of formaldehyde release that are suitable foruse in post-cure processing but without adverse effect on the wrinkleresistance, chlorine resistance, and hydrolysis resistance of thesubsequently cured fabric.

DEFINITIONS By free formaldehyde we mean the formaldehyde that ispresent but not bound and is therefore free to volatilize from solutionsof agents and from sensitized fabric. Free formaldehyde can bequantitatively determined conveniently by a titration method. Details ofa procedure for the determination of free formaldehyde are given byReid, Kullman, and Reinhardt in American Dyestuff Reporter, vol. 59, No.6, pp. 26-34, 1970.

The amount of formaldehyde release from a fabric is determined by a testmethod of the American Association of Textile Chemists and Colorists(AATCC Test Method 112-1968, Formaldehyde Odor in Resin Treated Fabric,Determination of: Sealed Jar Method, Technical Manual of the AATCC, vol.47, pp. 85-86, 1971). The standardized conditions of this test providethe means of obtaining comparative values of formaldehyde release fromfabrics finished by various treatments.

The term sensitized fabric is used in the textile finishing and garmentfabrication industries to denote the material at an intermediate stageof the post-cure finishing process. A sensitized fabric is one that (a)has been impregnated with a finishing agent, usually a methylol-amidetype crosslinking agent that is capable of producing durable pressproperties in cotton or cellulose-containing fabrics, and a catalyst forthe reaction between the finishing agent and the textile material, and(b) has been dried under conditions that do not cause any appreciablereaction between the finishing agent and the textile material. Thesensitized fabric is then ready for use in the post-cure durable pressprocess. The sensitized fabric is packaged and may be stored forprolonged periods before garment manufacture in which it is cut topattern, sewn, trimmed, then shaped by pressing to introduce creases,pleats, etc., and to smooth the garment in its final configuration. Thesensitized fabric in the form of the shaped garment is then cured,usually in an oven, to bring about the reaction of the finishing agentand the cellulosic component of the textile material of the garment andthus make the shaped configuration durable to wearing and laundering.Post-cure processing refers to that class of finishing treatments whichimpart durable press properties to the textile product through apostponed cure of the sensitized fabric after the textile product hasbeen made up into a garment or other apparel or household item. The termpost-cure processing is widely used in the textile industry; however,the terms deferred cure and delayed cure also have been applied to thistype of durable press process.

THE PROBLEM In the manufacture of post-cure durable press garments, aserious problem is the odor of formaldehyde from sensitized fabric whichcauses discomfort and sometimes is an actual health hazard to those whocut, sew, trim, and press the garment. This odor is due to the releaseof free formaldehyde from the fabric which can cause objectionableresponse--lachrymatory and sometimes allergenic from those who come intoproximity of the fabric. The same is true for those in the finishingplant who must handle solutions of the finishing agent that containexcessive amounts of free formaldehyde.

When packages of sensitized fabric are opened at the garment cuttingplant, the free formaldehyde therein is slowly released to createunpleasant and potentially unsafe working conditions. The presence of arecirculation air-conditioning system can intensify this problem. Thefree formaldehyde in the sensitized fabric is due to (a) residual orunreacted formaldehyde that was present in the finishing solution whenit was applied and has dried on the fabric; and (b) formaldehyde thathas been produced due to de-methylolation (reversal of the chemicalreaction by which the agent was prepared) of the methylolated amidecompound used in finishing. In the industry today, the problem of freeformaldehyde has restricted post-cure finishing mainly to one agent,dimethylol dihydroxyethyleneurea, which is available in solutions of lowfree formaldehyde content and which yield sensitized fabrics withmoderate levels of formaldehyde release. The industry, however, wouldlike to use other agents which may be more suitable, less expensive, orhave other desirable qualities but which at present are unusable becauseof formaldehyde release problems.

Among those agents that could be utilized advantageously in thepost-cure process, if formaldehyde release could be eliminated orreduced to an unobjectionable level, are the methylol carbamates. Theprimary source of free formaldehyde in fabric sensitized with carbamateagents is the excess formaldehyde which must be used in preparation ofthe finishing agent to maximize conversion of the carbamate to thedimethylol derivative. Stability of the methylolated carbamate agent inthe sensitized 0 fabric to de-methylolation during storage has beendemonstrated to be excellent.

3 THE PRIOR ART In the prior art various means have been proposed forreducing the free formaldehyde content of finishing agents. Albeit manyproposed methods are successful In decreasing the amount of freeformaldehyde, elimination of some desirable characteristic of the finishor the introduction of an undesirable effect is often a consequence ofthe action.

For example, it has been suggested by Frich and Reinhardt, AmericanDyestuff Reporter, vol. 56, No. 9, p. 41, Apr. 24, 1967, that by use oflower molar ratios of formaldehyde to carbamate in synthesis, agents canbe prepared which release less formaldehyde fumes in durable pressprocessing. However, this improvement is achieved at the expense of alower level of chlorine resistance in the finished fabrics.

Another approach to decreased free formaldehyde has been the treatmentof the solution of the methylolated finishing agent with a chemicalreactant that combines with the free formaldehyde and thus binds it fromrelease during fabric processing. Although successful in controllingfree formaldehyde, undesirable collateral effects on the finishedfabrics have been produced by this chemical technique, principallydecreased durability and substantially decreased chlorine resistance ofthe finish upon hydrolysis and severe laundering. Chemical methods ofthis type have been disclosed by Reid, Kullman, and Reinhardt inAmerican Dyestuff Reporter, vol. 59, No. 6, pp. 26-28, 32, and 34, 1970,by Weiland in US. Pat. 3,590; 100, and by Bertini and Edmondson in US.Pat. 3,597,- 380. The principal fault with these chemical methods liesin the fact that the free formaldehyde is bound through some chemicalreaction but remains in the solution of finishing agent. In this type ofmodification, extraneous materials are thus applied to the textilesubstrate along with the desired finishing agent and become bound in thefinish. These extraneous materials impart properties andsusceptibilities that are different than those of the finish produced bythe finishing agent being used.

OBJECTS OF THE PRESENT INVENTION HOW THE OBJECTIVES ARE ACHIEVED Theobjects of the present invention are achieved by removing freeformaldehyde from solutions of methylolated carbamate finishing agentsby reaction of the free formaldehyde with phthalimide. The chemicalreaction may be represented by the following equation:

(:1: \NH+ HCHO \NOHZOH ii i The product of the reaction, thephthalimide-formaldehyde adduct (also called N-methylol phthalimide andN- arated from the solution. After separation, the adduct can bedissociated so that the phthalimide can be recovered for subsequentreuse which, of course, is advantageous from an economic viewpoint.

Separation of the adduct from the methylol carbamate solution completelyand irreversably removes the free formaldehyde. This is unlike thosemethods in which the free formaldehyde is bound through formation of asoluble adduct which remains in the solution and is thus sub ject toreversion to regenerate the free formaldehyde. Furthermore, with asoluble adduct in a solution of finishing agent, a foreign material ispresent that can react with the cellulose during the textile finishingtreatment. Such reaction introduces other, often undesirable, propertiesand susceptibilities along with those desired from the finishing agentemployed. In the process of the present invention, separation of theinsoluble phthalimide-formaldehyde adduct from the solution of thefinishing agent precludes the introduction of such extraneous effects inthe finishing treatment.

Textile materials sensitized by treatment with carbamate finishingagents with free formaldehyde removed by the process of the instantinvention have greatly diminished formaldehyde release values. Thesensitized fabrics when cured yield wrinkle resistant fabrics with theexcellent chlorine resistance and hydrolysis resistance that arecharacteristic of carbamate finishes. There are no undesirablecollateral properties introduced as no extraneous material is presentalong with the carbamate finishing agent.

Use of solutions of methylolated carbamates with free formaldehyderemoved by the process of this invention eliminates the need for extracare in handling, expensive safety equipment, and special processingmethods to avoid pollution of the surrounding atomsphere by the noxiousfumes of formaldehyde during preparation of treatment baths andsubsequent finishing of fabric. The necessity is minimized for extraprecautions to protect workers from inhalation of noxious formaldehydefumes during application of finishing solutions to textile materials,during drying operations in sensitization, during handling of thesensitized fabric in warehousing and in garment fabrication, and incuring operations to accomplish final finishing of the fabric.

SCOPE OF THE INVENTION Textile materials which can be treated withfinishing agents modified by the process of this invention includecellulose fibers, yarns, fabrics, and the like. The fabrics can 'bewoven, knitted, or nonwoven. The cellulose may be natural, such ascotton, linen, ramie, and the like, or regenerated, such as viscose andother types of rayon. In addition to textile materials consisting whollyof cellulose, those in which cellulose fibers are blended with syntheticfibers can be treated. Among these, particularly amenable are blendsthat contain cotton and polyester fibers.

Treatment of the textile materials with finishing agents modified by theprocess of this invention may be carried out by any of those methods inwhich methylolated agents are employed to impart wrinkle resistance anddurable press properties. No changes in treatments are necessary toaccommodate use of these finishing agents in which free formaldehyde hasbeen removed. The finishing agents of this invention are particularlysuited to post-cure processing because of the low formaldehyde releasefrom sensitized fabrics so-treated. The amount and type of finishingagents, catalyst, chemical auxiliaries, and the treatment conditions,and other variables of chemical finishing processes for producingwrinkle resistant cellulosic textiles known to those skilled in the artare not affected by use of agents from which free formaldehyde has beenremoved by the process of this invention.

Free formaldehyde is removed from the solution of finishing agent byaddition of phthalimide to the solution. A reaction between the freeformaldehyde and phthalimide occurs to give an insoluble adducts asshown in the above cited chemical equation. The pH of the solution mustbe below about 8. Preferably, the pH should be below 7. Other imidesthat yield insoluble formaldehyde adducts can be employed similarly inthe process of this invention. The insoluble adduct is separated fromthe solution of finishing agent by filtering, decanting, or any otherconvenient technique. Removal of the adduct from the solution offinishing agent removes the free formaldehyde which has reacted with thephthalimide to produce the adduct. By adjustment of the amount ofphthalimide added to the solution of finishing agent, the amount of freeformaldehyde removed can be adjusted. That is, ideally, one mole ofphthalimide is needed for complete removal of each mole of freeformaldehyde present in the solution of finishing agent. In actualpractice, as is the case in most reactions of organic chemistry, aslight excess of phthalimide is necessary to react with all the freeformaldehyde. However, if complete removal of free formaldehyde is notneeded but merely reduction of the amount to a specified level, lessphthalimide than that chemically euqivalent to the free formaldehyde canbe employed. Thus, the operator has the means of decreasing the level offree formaldehyde as desired.

This invention is directed particularly at removal of free formaldehydefrom solutions of methylolated carbamate finishing agents. Among suchagents are the methylol derivatives of alkyl carbamates such as methyl,ethyl, propyl, butyl, and the like, methylolated derivatives ofhydroxyalkyl carbamates such as hydroxyethyl, hydroxypropyl and thelike, and methylolated derivatives of alkoxyalkyl carbamates such asmethoxyethyl, methoxypropyl and the like. In principle, the invention isapplicable to other methylol type finishing agents such as the methylolderivatives or ureas, modified ureas including ethyleneureas,dihydroxyethyleneureas, propyleneureas, urons, triazones, and the like,and triazines.

SUMMARY OF THE INVENTION In summary, this invention makes available amethod whereby free formaldehyde is removed from a solution of finishingagent. The solution is treated with phthalimide which reacts with thefree formaldehyde to produce an insoluble phthalimide-formaldehydeadduct that can be separated from the solution and thus remove the freeformaldehyde. Not only does separation of the phthalimide-formaldehydeadduct remove free formaldehyde but it assures that there are noundesirable side efi'ects of subsequently finished fabrics from suchremoval as are often experienced when other chemical methods areemployed for decreasing the level of free formaldehyde in the finishingagent solution. Sensitized fabrics produced by use of the finishingagents of this invention have low formaldehyde release values and uponpost-curing yield wrinkle resistant fabrics without impairment of theother properties characteristically produced by the finishing agent. Theinvention provides a route to the production of methylolated carbamatefinishing agents with low free formaldehyde content which makes theseagents attractive and practical for greater utilization in the importantpost-cure process for durable press finishing.

The following examples must not be construed as limiting the scope ofthe invention but are given to illustrate its teachings. Numerousmodifications Within the spirit of the invention will become apparent tothose skilled in the art.

EXAMPLE 1 To 30 parts of a 50% (wt/Wt.) aqueous solution of dimethylolmethyl carbamate (Solution A) that had a strong odor of formaldehyde wasadded 8.8 parts of phthalimide. The mixture was heated to 167 F. withstirring until solubilization of the phthalimide occurred, then held at158-167 F. for five minutes. On cooling to room temperature,precipitation of the phthalimide-formaldehyde adduct occurred. Thesolution was filtered; no

strong odor of formaldehyde was evident in the filtrate (Solution B).

EXAMPLE 2 Portions of Solutions A and B of Example 1 were analyzed forfree formaldehyde content by the aforementioned procedure of Reid,Kullman, and Reinhardt. The results were:

Percent free form- Solution: aldehyde A 5.0

EXAMPLE 3 Two solutions were prepared for the treatment of fabricconsisting of:

Solution C 20 parts of Solution A (Ex. 1) 0.6 part of Zn(NO -6H O 79.4parts of water Solution D 20 parts of Solution B (Ex. 1) 0.6 part ofZn(NO -6H O 79.4 parts of water Samples of cotton printcloth wereimpregnated with these solutions and the excess squeezed oif, and theprocess Was repeated to ensure thorough impregnation. The wet,impregnated fabrics were sensitized by drying in an oven at 140 F. for 7minutes. Immediately after sensitization a weighed portion of eachfabric was suspended above 50 ml. of distilled water in a glass jar andthe jar sealed. The jars were placed in an oven at F. (49 C.) for 20hours as specified in AATCC Test Method 112l968 and the formaldehyderelease subsequently determined. Fabric sensitized with Solution Creleased 5800 ppm. of formaldehyde and fabric sensitized with Solution Dreleased only 2200 ppm.

It can be readily noted that sensitization treatment with Solution Dresulted in a substantially lower formaldehyde release value than thatof sensitization treatment with Solution C. This illustrates thatremoval of free formaldehyde from the dimethylol methyl carbamatesolution through formation and separation of the phthalimideformaldehydeadduct gives a solution with lowered free formaldehyde content and useof this solution for sensitization gives a sensitized fabric with asubstantially lowered level of formaldehyde release.

EXAMPLE 4 Portions of the sensitized fabrics of Example 3 were cured inan oven for 3 minutes at 320 F., then washed and dried. To determineresistance to acid hydrolysis of the finished fabrics, portions of eachwere treated with a solution buffered to pH 3.2 for 30 minutes at 104F., then washed and dried. It is known that hydrolysis of this type doesnot affect a carbamate finish but causes susceptibility to chlorinedamage in a finish produced by treatment with a carbamate agent modifiedwith ethyleneurea for decreased free formaldehyde content (cf. Table IVand related discussion in the previously cited paper by Reid, Kullmanand Reinhardt).

Properties of the fabrics of the present example before and afterhydrolysis are given in Table I. Conditioned wrinkle recovery (WRA) wasdetermined by the procedure of AATCC Test Method 66-1968; wet wrinklerecovery was determined following the same procedure on wet specimensthat had been blotted to remove excess moisture. Resistance to chlorinedamage was determined by AATCC Test Method 92-1967.

TABLE I WRA, (W-l-F), deg. Str. retention in chlor.-scorch TreatmentCond. Wet test, percent Solution Cured (before hydrolysis)- 281 271 100Cured (after hydrolysis) 274 270 100 Solution D:

Cured (before hydrolysis) 274 265 100 Cured. (after hydrolysis). 270 27394 The properties of fabric finished with Solution D are as good asthose of fabric finished with Solution C. This shows that phthalimidetreatment of dimethylol methyl carbamate solution to reduce the freeformaldehyde content and to lower formaldehyde release from thesensitized fabric has no adverse effect on the properties of the curedfabric.

We claim:

1. A process for the treatment of cellulose containing textiles to givewrink1e-, acid-, and chlorination-scorch resistance properties whichcomprises:

(a) preparing a treatment bath consisting of:

(i) about from 0.3 to 1.0 part of zinc nitrate hexahydrate;

(ii) about from 8 to 20 parts of the solution resulting after separationof the insoluble adduct produced by reaction of about 8.8 parts ofphthalimide with the free formaldehyde present in about 30 parts of a50% (wt/wt.) aqueous dimethylol methyl carbamate, and;

(iii) sufiicient water to make 100 parts (b) impregnating a cellulosiccontaining textile with the solution of step (a);

(c) sensitizing the impregnated fabrics by heating at 140 F. for 7minutes; and

(d) curing the sensitized fabric of step (c) by heating at 320 F. for 3minutes.

2. The sensitized cellulose containing textile product prepared by theprocess which comprises:

(a) preparing a treatment bath consisting of:

(i) about from 0.3 to 1.0 part of Zinc nitrate hexahydrate;

(ii) about from 8 to 2 0 parts of the solution resulting after theseparation of the insoluble adduct produced by reaction of about 8.8parts of phthalirnide with the free formaldehyde present in about partsof a (Wt/wt.) aqueous dimethylol methyl carbamate; and

(iii) sufficient water to make parts;

(b) impregnating a cellulosic containing textile with the solution ofstep (a); and (c) sensitizing the impregnated fabric by heating at F.for 7 minutes. 3. The textile product prepared by the process of claim1.

References Cited UNITED STATES PATENTS 6/1972 Weiland 8116.3 8/1971Bertini et al 8-116.3 X

OTHER REFERENCES GEORGE F. LESMES, Primary Examiner 30 J. CANNON,Assistant Examiner

